Pakistani Taliban on Saturday claimed responsibility for holding up to 25 boys hostage as punishment for tribesmen who supported the military in the country's troubled northwest.

Pakistani officials said on Friday militants in Afghanistan kidnapped the boys after they mistakenly crossed the border while on an outing in the border tribal region of Bajaur on Wednesday.

A Pakistani Taliban spokesman said they held the boys, and their fate would be decided by the militants from Bajaur.

"We have kidnapped them as their parents and tribal elders are helping the government and are fighting against us," spokesman Ehsanullah Ehsan told Reuters from an undisclosed location.

He said they held between 20 to 25 boys, but did not say where they have been kept. Bajaur's top government administrator, Islam Zeb, said 25 boys were missing.

A group of around 60 boys took part in the outing but about 20 below ten years old were allowed to return to Pakistan, while up to 40 others between 12 to 14 years old were held, officials said earlier.

Ehsan said they had a plan of mass-scale kidnappings and expected people in large number to visit the border region on Eid al-Fitr, a Muslim holy festival that was celebrated this week, marking the end of the fasting month of Ramadan.

Security officials said they learned of the kidnappings when the parents of the children, members of a tribe that inhabits the frontier area, informed them of the abductions on Friday.

A Pakistani cabinet minister said the interior ministry was in contact with the Afghan officials on the issue.

"The incident happened on their side and, as per law, it is  responsibility of the Afghan government to ensure their safe return to Pakistan," Shaukat Ullah, federal minister for States and Frontier Regions, told Reuters.

The boys belonged to tribesmen from Mamoun who are opposed to al Qaeda and the Taliban and have raised militias to fight them, angering militants who often hit back with bombings and shooting attacks.

Bajaur is opposite the eastern Afghan province of Kunar and has long been an infiltration route for militants entering Afghanistan to fight US-led forces there.

Hundreds of Pakistani militants fled to Kunar in the face of Pakistani military offensives in Bajaur, officials say. – Reuters